1. Field of the Invention
This invention relates to a copying apparatus in which both the copying mode and the copying magnification can be changed over. The copying mode refers to a copying style in which an original supporting table capable of supporting thereon a three-dimensional original such as a book is used and the original on this table is scanned by a scanning optical system to obtain a copy, or a copying style in which a thin sheet-like original is moved by a sheet conveying device such as rollers, whereby the original is scanned to obtain a copy, and for the sake of simplicity, the former is referred to as the book mode copying and the latter is referred to as the sheet mode copying.
2. Description of the Prior Art
An example of the copying apparatus as described above is disclosed in Japanese Laid-open patent application No. 48323/1977. The apparatus described in this publication is such that during the book mode copying, an original resting on an original supporting table is scanned by two reciprocally movable mirrors and during the sheet mode copying, said two mirrors are stopped below one end of the original supporting table while, on the other hand, a sheet conveying device is installed at said one end of the original supporting table and the image of a sheet original conveyed by the conveying device is projected upon a photosensitive medium through the agency of said two mirrors. During reduction copying, irrespective of the book mode copying or the sheet mode copying, a mirror for extending the length of the optical path is inserted behind said two mirrors. The disadvantages of the apparatus of this publication are that since the auxiliary mirror is used during reduction copying as described above, a loss of quantity of light is caused by that mirror, that since part of the original supporting table must also be used during the sheet mode copying as described above, conveyance of the original is liable to become unstable and that as described above, the original conveying device must be moved in accordance with the change-over of the copying mode and this results in complication of the construction and cumbersomeness of the operation.
Another example of the apparatus is disclosed in Japanese Laid-open patent application No. 31746/1977. In the apparatus of this publication, the book mode copying is effected by scanning the original on the original supporting table by two reciprocally movable mirrors and the sheet mode copying is effected by conveying an original through a window portion provided at a predetermined position to which said two scanning mirrors are not opposed, and at this time, a second one of said two mirrors is turned by a predetermined angle so as to be retracted out of the optical path between said window portion and a lens. When the copying magnification is changed, the lens is displaced in a direction along the optical axis. This apparatus has not the disadvantages perculiar to the first-mentioned known apparatus, but a complex mechanism is necessary to cause the mirror reciprocated for the scanning of the original on the original supporting table to be turned at a predetermined position for the sheet mode copying and in addition, such mechanism is weak and low in accuracy.